Vulnerability of shallow ground water and drinking-water wells to nitrate in the United States: Model of predicted nitrate concentration in U.S. ground water used for drinking (simulation depth 50 meters) -- Input data set for fresh surface water withdrawal (gwava-dw_swus)

This data set represents the amount of fresh surface water withdrawal for irrigation, in megaliters per day, in the conterminous United States. The data set was used as an input data layer for a national model to predict nitrate concentration in ground water used for drinking. Nolan and Hitt (2006) developed two national models to predict contamination of ground water by nonpoint sources of nitrate. The nonlinear approach to national-scale Ground-WAter Vulnerability Assessment (GWAVA) uses components representing nitrogen (N) sources, transport, and attenuation. One model (GWAVA-S) predicts nitrate contamination of shallow (typically less than 5 meters deep), recently recharged ground water, which may or may not be used for drinking. The other (GWAVA-DW) predicts ambient nitrate concentration in deeper supplies used for drinking. This data set is one of 14 data sets (1 output data set and 13 input data sets) associated with the GWAVA-DW model. Full details of the model development are in Nolan and Hitt (2006). For inputs to the model, spatial attributes representing 13 nitrogen loading and transport and attenuation factors were compiled as raster data sets (1-km by 1-km grid cell size) for the conterminous United States (see table 1). >Table 1.-- Parameters of nonlinear regression model for > nitrate in ground water used for drinking (GWAVA-DW) > and corresponding input spatial data sets. > [kg, kilograms; km2, square kilometers.] > >Nitrogen Source Factors Data Set Name > 1 farm fertilizer (kg/hectare) gwava-dw_ffer > 2 confined manure (kg/hectare) gwava-dw_conf > 3 orchards/vineyards (percent) gwava-dw_orvi > 4 population density (people/km2) gwava-dw_popd > >Transport to Aquifer Factors > 5 water input (km2/cm) gwava-dw_wtin > 6 glacial till (yes/no) gwava-dw_gtil > 7 semiconsolidated sand aquifers gwava-dw_semc > (yes/no) > 8 sandstone and carbonate rocks gwava-dw_sscb > (yes/no) > 9 drainage ditch (km2) gwava-dw_ddit > 10 Hortonian overland flow gwava-dw_hor > (percent of streamflow) > >Attenuation Factors > 11 fresh surface water withdrawal gwava-dw_swus > for irrigation (megaliters/day) > 12 irrigation tailwater recovery (km2) gwava-dw_twre > 13 Dunne overland flow gwava-dw_dun > (percent of streamflow) > 14 well depth (meters) - "Farm fertilizer" is the average annual nitrogen input from commercial fertilizer applied to agricultural lands, 1992-2001, in kilograms per hectare. "Confined manure" is the average annual nitrogen input from confined animal manure, 1992 and 1997, in kilograms per hectare. "Orchards/vineyards" is the percent of orchards/vineyards land cover classification. "Population density" is 1990 block group population density, in people per square kilometer. "Water input" is the ratio of the total area of irrigated land to precipitation, in square kilometers per centimeter. "Glacial till" is the presence or absence of poorly sorted glacial till east of the Rocky Mountains. "Semiconsolidated sand aquifers" is the presence or absence of semiconsolidated sand aquifers. "Sandstone and carbonate rocks" is the presence or absence of sandstone and carbonate rock aquifers. "Drainage ditch" is the area of National Resources Inventory surface drainage, field ditch conservation practice, in square kilometers. "Hortonian overland flow" is infiltration excess overland flow estimated by TOPMODEL, in percent of streamflow. "Fresh surface water withdrawal for irrigation" is the amount of fresh surface water withdrawal for irrigation, in megaliters per day. "Irrigation tailwater recovery" is the area of National Resources Inventory irrigation system, tailwater recovery conservation practice, in square kilometers. "Dunne overland flow" is saturation overland flow estimated by TOPMODEL, in percent of streamflow. "Well depth" is the depth of the well, in meters. Well depth was not compiled as a spatial data set. Well depth equals 50 meters for the model simulation being presented. Reference cited: Nolan, B.T. and Hitt, K.J., 2006, Vulnerability of shallow ground water and drinking-water wells to nitrate in the United States: Environmental Science and Technology, vol. 40, no. 24, pages 7834-7840.本数据集记录了美国本土范围内用于灌溉的新鲜地表水取水量，单位为兆升/日。 该数据集曾作为全国性模型的输入数据图层，用于预测饮用水源地下水的硝酸盐浓度。 Nolan与Hitt（2006）开发了两款全国性模型，用以预测非点源硝酸盐对地下水的污染。其中，适用于全国尺度的地下水脆弱性评价（Ground-WAter Vulnerability Assessment, GWAVA）非线性方法，涵盖了氮（N）源、输运与衰减三类表征组分。 其中一款模型（GWAVA-S）用于预测浅层（通常深度小于5米）、新近补给地下水的硝酸盐污染情况，此类地下水可被用作饮用水源，亦可不作饮用水源使用。另一款模型（GWAVA-DW）则用于预测可供饮用的深层地下水的环境硝酸盐浓度。 本数据集是与GWAVA-DW模型相关的14个数据集之一（含1个输出数据集与13个输入数据集）。模型开发的完整细节可参见Nolan与Hitt（2006）的研究成果。 针对该模型的输入数据，研究人员针对美国本土整合了13项表征氮负荷、输运与衰减因子的空间属性数据，以栅格数据集形式存储（网格单元尺寸为1千米×1千米），详见表1。 >表1.-- 饮用水源地下水硝酸盐非线性回归模型（GWAVA-DW）参数及对应输入空间数据集 > [kg，千克；km²，平方千米。] > >氮源因子 数据集名称 > 1 农田化肥（千克/公顷） gwava-dw_ffer > 2 圈养畜禽粪便（千克/公顷） gwava-dw_conf > 3 果园/葡萄园占比（百分比） gwava-dw_orvi > 4 人口密度（人/平方千米） gwava-dw_popd > >含水层输运因子 > 5 水输入量（平方千米/厘米） gwava-dw_wtin > 6 冰碛物分布（是/否） gwava-dw_gtil > 7 半固结砂岩含水层分布（是/否）gwava-dw_semc > 8 砂岩与碳酸盐岩含水层分布（是/否）gwava-dw_sscb > 9 排水沟渠面积（平方千米） gwava-dw_ddit > 10 霍顿坡面流占径流量百分比 gwava-dw_hor > >衰减因子 > 11 灌溉用新鲜地表水取水量（兆升/日）gwava-dw_swus > 12 灌溉尾水回收面积（平方千米）gwava-dw_twre > 13 邓恩坡面流占径流量百分比 gwava-dw_dun > 14 井深（米） - "农田化肥"指1992-2001年间施用于农田的商用化肥年均氮输入量，单位为千克/公顷。 "圈养畜禽粪便"指1992年与1997年的圈养畜禽粪便年均氮输入量，单位为千克/公顷。 "果园/葡萄园占比"指土地覆盖分类中果园与葡萄园的占比百分比。 "人口密度"指1990年街区组人口密度，单位为人/平方千米。 "水输入量"指灌溉土地总面积与降水量的比值，单位为平方千米/厘米。 "冰碛物分布"指落基山脉东侧是否存在分选较差的冰碛物。 "半固结砂岩含水层分布"指是否存在半固结砂岩含水层。 "砂岩与碳酸盐岩含水层分布"指是否存在砂岩与碳酸盐岩含水层。 "排水沟渠面积"指《国家资源清查》中地表排水、田间沟渠保护措施的面积，单位为平方千米。 "霍顿坡面流"指由TOPMODEL估算的超渗坡面流，以占径流量的百分比表示。 "灌溉用新鲜地表水取水量"指用于灌溉的新鲜地表水取水量，单位为兆升/日。 "灌溉尾水回收"指《国家资源清查》中灌溉系统尾水回收保护措施的面积，单位为平方千米。 "邓恩坡面流"指由TOPMODEL估算的饱和坡面流，以占径流量的百分比表示。 "井深"指水井深度，单位为米。井深未被整合为空间数据集，在本次展示的模型模拟中，井深统一取值为50米。 引用文献： Nolan, B.T. 与 Hitt, K.J., 2006, 《美国浅层地下水与饮用水井对硝酸盐的脆弱性》，《环境科学与技术（Environmental Science and Technology）》，第40卷第24期，第7834-7840页。